In recent years, the development of heat storing devices designed to achieve effective use of energy by transferring heat energy stored in a heat storing material to a heat exchange fluid such as cooling water has been being pursued. For example in an engine, whereas a lot of waste heat is produced while the engine is running, if heat is transferred to the engine at the time of starting, starting becomes smooth. By employing a heat storing device, it is possible to store waste heat while the engine is running and use it to warm up the engine at the time of starting. Various technologies for raising the heat exchange efficiency of this kind of heat storing device are known, as shown in JP-A-2004-271119 and JP-A-2003-336979.
Various technologies for raising the heat exchange efficiency of ordinary heat exchangers are also known, as shown in JP-A-5-149687.
The outline of a heat storing device disclosed in JP-A-2004-271119 will be described with reference to FIG. 22A to FIG. 22C, the outline of a heat storing device disclosed in JP-A-2003-336979 will be described with reference to FIG. 23A to FIG. 23C, and the outline of a heat storing device disclosed in JP-A-5-149687 will be described with reference to FIG. 24A and FIG. 24B.
FIG. 22A is a sectional view of a first heat storing device of related art, FIG. 22B is a plan view of a heat exchange plate and a double pipe shown in FIG. 22A, and FIG. 22C is a sectional view of a heat exchange plate shown in FIG. 22A.
In the first heat storing device of related art 200 shown in FIG. 22A to FIG. 22C, multiple annular heat exchange plates 202 are stacked with many spacers 203 between them inside a cylindrical sealed tank 201, and a double pipe 204 passes through the heat exchange plates 202 at the center of the cylindrical sealed tank 201. Internal spaces formed in the heat exchange plates 202 are filled with a heat storing material Ah (see FIG. 22C).
A fluid Flu introduced through an inlet 205 enters the outer pipe 206 of the double pipe 204 and flows radially outward through many openings in the outside of the outer pipe 206 as shown by the arrows f1, flows through the gaps 207 between the heat storing plates 202, 202 and exchanges heat with the heat storing material Ah, ascends as shown by the arrows f2 and enters the inner pipe 208 of the double pipe 204, and is guided out through an outlet 209.
With this heat storing device 200, by the fluid Flu flowing through the gaps 207 being disrupted by the many spacers 203, the efficiency of the heat exchange between the heat storing material Ah and the fluid Flu can be increased to some extent.
However, because the fluid Flu is just made to strike small semi-spherical spacers 203 projecting from the surfaces of the heat storing plates 202, it is not easy for the fluid Flu to be made turbulent. Thus, in raising the heat exchange efficiency with this kind of construction, there is room for improvement. To raise the heat exchange efficiency of the heat storing device 200 more, it is conceivable for example to employ technology disclosed in JP-A-2004-271119 and JP-A-2003-336979.
FIG. 23A shows schematically a second heat storing device of related art, FIG. 23B is a sectional view of the heat storing device shown in FIG. 23A, and FIG. 23C is an exploded view of a main part of the heat storing device shown in FIG. 23A.
As shown in FIG. 23A to FIG. 23C, this second heat storing device of related art 300 has multiple flat, plate-shaped units 302 stacked inside a sealed tank 301. The units 302 each consist of three plates in a stack, namely a first plate 303, a second plate 304 and a third plate 305.
These plates 303, 304 and 305 respectively have flat recesses 303a, 304a and 305a in their upper faces. The recess 303a in the first plate 303 forms a heat exchange material space 306, the recess 304a in the second plate 304 forms a waste heat hot water passage 307, and the recess 305a in the third plate 305 forms a supply hot water passage 308.
As shown in FIG. 23C, the recess 303a in the first plate 303 has a first heat transfer fin 311, the recess 304a in the second plate 304 has a second heat transfer fin 312, and the recess 305a in the third plate 305 has a third heat transfer fin 313. These heat transfer fins 311 to 313 are corrugated in shape.
As shown in FIG. 23B, waste heat hot water We flowing through the waste heat hot water passage 307 can exchange heat with a heat storing material Ah inside a heat exchange material space 306 while exchanging heat with supply hot water Wi flowing through the supply hot water passage 308. The supply hot water Wi flowing through the supply hot water passage 308 can exchange heat with a heat storing material Ah in a heat exchange material space 306 while exchanging heat with the waste heat hot water We.
With this heat storing device 300, by providing the first, second and third heat transfer fins 311 to 313, it is possible to increase the heat exchange efficiency to some extent. However, because the heat transfer fins 311 to 313 are provided, the manufacturing cost increases. By an amount corresponding to the heat transfer fins 311 to 313, the heat storing device 300 as a whole becomes large and its weight increases. Furthermore, because fluids (namely the waste heat hot water We and the supply hot water Wi) are being made to pass between large heat transfer fins 312 to 313, compared to the degree of the improvement in heat exchange efficiency, the degree of the increase in fluid pressure loss is extremely large.
FIG. 24A is a schematic exploded view of a heat exchanger of related art, and FIG. 24B is a sectional view of the heat exchanger shown in FIG. 24A.
As shown in FIG. 24A and FIG. 24B, this heat exchanger of related art 400 has an upper/lower pair of heat transfer plates 401, 401 brought face-to-face with each other across a fixed space 402 fluid passage 402). The upper/lower pair of heat transfer plates 401, 401 each have many thinly sliced heat transfer fins 403 extending across the fluid passage 402 to the proximity of the other plate 401. In this way, the heat transfer plates 401, 401 and the heat transfer fins 403 can be given a large heat transfer area with respect to the fluid flowing through the fluid passage 402.
With this heat exchanger 400, by the heat transfer fins 403 being made to incline regularly in the flow direction of the fluid and the opposite direction, turbulence can be created in the fluid passing between the heat transfer fins 403. As a result, the heat exchange efficiency can be raised.
However, with a heat exchanger 400 like this, because many thinly sliced heat transfer fins 403 are provided on upper and lower heat transfer plates 401, 401, the manufacturing cost increases. By an amount corresponding to the many heat transfer fins 403, the heat exchanger 400 as a whole becomes large and its weight increases. Furthermore, because a fluid is made to pass between large heat transfer fins 403, compared to the degree of the improvement in heat exchange efficiency, the degree of the increase in fluid pressure loss is extremely large.
As is clear from the foregoing explanation, the technology of the heat storing device 300 of related art shown in FIG. 23A to FIG. 23C or the heat storing device 400 of related art shown in FIG. 24A and FIG. 24B cannot be employed as it is in the heat storing device 200 of related art shown in FIG. 22A to FIG. 22C, and there is room for further improvement.
Accordingly, technology has been awaited with which it is possible greatly to increase the efficiency of heat exchange between the heat storing material and the fluid while making the heat storing device low-cost and minimizing fluid pressure losses.